I assume the file is on the server where the applet resides, and not on the client machine?

The Apache POI library can read Excel files. You would create an HSSFWorkbook object from the file input stream, and then use the getSheet method to obtain a reference to the sheet you want to display. The sheet's getRow method gives you a reference to a row of cells, from which you can call getCell to get the contents of any particular cell.